Iron-catalyzed Autoxidation of Cholesterol in the Presence of Unsaturated Long-chain Fatty Acid

概要

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Oxy-functionalization of cholesteryl acetate (1a) occurred, giving 3β-acetoxy-5,6-epoxycholestane (2a), 3β-acetoxycholest-5-en-7-one (3a), 3β-acetoxycholest-5-en-7-ol (4a), and an unidentified product (5), when 1a was oxidized by a system consisting of Fe (acac)_3 and the hydroperoxide of an unsaturated long-chain fatty acid (LH) such as oleic, linolic, or linolenic acid (Table I). The epoxidation of stilbene by the same system was found to be non-stereospecific. These results and the fact that the reaction in this system was inhibited by a radical scavenger (BHT) were fairly compatible with those obtained with the Fe (acac)_3-^tBuOOH system, which is assumed to generate oxy and peroxy radicals. Autoxidation of 1a and cholesterol (1b) in the presence of Fe (acac)_3 and LH proceeded after a time-lag of several hours and was also inhibited by BHT. The marked stereoselectivity of β-epoxidation (β/α+β=0.72) and the extent (about 30-40%) of allylic oxidation in the autoxidation were in fair agreement with those found for 1a in the Fe(acac)_3-LOOH system (Table II). Autoxidation of stilbene in the presence of Fe (acac)_3 and LH also led to non-stereospecific epoxidation. Thus, the autoxidation of cholesterols (1a and 1b) in the Fe (acac)_3-LH system was assumed to be a radical reaction in which LOO・and LO・are the attacking species.
社団法人日本薬学会の論文
1982-09-25